Wired to a polygraph, South Korean lobbyist Tongsun Park was undaunted by charges that he had sought to bribe dozens of congressmen during the so-called Koreagate scandal in the 1970s.
Defense lawyer William G. Hundley, sitting alongside Park at his questioning by an FBI polygrapher, marveled at his client’s ability to shield lawmakers he considered friends. “The needle never moved,” said Hundley, recalling how Park denied payment after payment without the polygraph registering any deception.
Park, however, later admitted many of his cash gifts, testified before a grand jury and even became a star witness at House Ethics Committee hearings into the scandal.
The incident left an indelible mark on Hundley, a man long skeptical about polygraphs who has practiced criminal law for 30 years after serving as a Justice Department official under Robert F. Kennedy.
“I don’t think there’s any medical or scientific evidence which ever tends to establish that your blood pressure elevates, that you perspire more freely or that your pulse quickens when you tell a lie,” Hundley said.
Amid a growing disenchantment with the value of polygraphs, others are adopting Hundley’s views. Congress banished most of their uses in private industry six years ago. And, although the FBI, CIA and National Security Agency still use them routinely to screen employees, the recent Aldrich H. Ames espionage case is leading CIA officials to rely on polygraphs a little less. It also has spurred another round of controversy over their accuracy and the dangers of relying on them.
The idea of detecting liars by observing their behavior has roots in ancient history. In Asia, an interrogation method involved scientific principles based on the lessening of salivation under nervous tension. When the mouths of several suspects were filled with dry rice, the suspect exhibiting the greatest difficulty spitting out the rice was judged guilty.
Another precursor of the polygraph was said to have been used in India. Suspects were sent into a dark room and told to pull the tail of a sacred donkey. They were warned that if the animal brayed, this signaled their guilt.
Unknown to the suspects, the donkey’s tail had been dusted with black powder. Those with a clear conscience pulled the tail, while the guilty individuals did not. An examination of the suspects’ hands revealed those with a guilty conscience.
The polygraph came along in 1921, invented by John A. Larson, a University of California medical student working with help from a police official. The device ostensibly detects when a person is lying by monitoring and recording certain body changes affected by a person’s emotional condition.
Today’s more refined versions continuously record blood pressure, pulse and respiration. It records these conditions simultaneously, tracing them with squiggly lines on graph paper--thus the name polygraph .
Law enforcement and intelligence agencies have long considered the device an invaluable aid, although they do not rely upon it exclusively. Most investigators view it as a useful tool when applied in conjunction with other investigative techniques. Sometimes they use the mere threat of a polygraph test to achieve leverage with suspects.
But even with a limited use, the reliability of “the box” has long been disputed by psychologists and criminal justice authorities. Very few federal or state judges permit the use of polygraph results in court.
Many states specifically have barred their introduction in court--including California, where the state Supreme Court has outlawed them even when opposing lawyers agree to such evidence.
Defense lawyer Richard Ben-Veniste, a former associate prosecutor from the Watergate scandal of two decades ago, said the polygraph “is a useful tool for ordinary people but not for those in counterintelligence who know how to beat it.”
Defense attorney Plato Cacheris called it “a great psychological tool” in most cases. “You take the average guy and tell him you’re going to give him a poly, and he’s concerned enough to believe that it will disclose any deception on his part,” Cacheris said.
Cacheris’ latest client, CIA spy Ames, apparently understood the machine’s limitations. He passed a CIA polygraph in 1991 after his answers were judged “questionable” on an initial test when asked about his signs of newfound wealth. Ames was sentenced to life in prison after pleading guilty to receiving about $2.5 million from his Russian handlers for selling U.S. secrets over a period of more than eight years.
The late Sen. Sam J. Ervin Jr. (D-N.C.), a self-described “country lawyer” who was chairman of the 1973 Senate Watergate Committee, often ridiculed polygraphs as “modern witchcraft.”
Critics say the machines can be fooled by inveterate liars who no longer react emotionally to lying, by people who take certain drugs beforehand or by those who have wholly convinced themselves that their lies are the truth. In all those instances, the person being questioned would show little, if any, of the measurable reactions normally associated with lying.
Other critics assert that a person can raise his own blood pressure to confuse the test by pressing his toes hard against the floor on questions where he is known to be telling the truth.
But Paul Minor, who retired in 1987 as chief polygrapher for the FBI, scoffed at some of these suggestions.
“Can the machine be defeated? Yes, but not easily,” Minor said.
“When the poly is beaten, it’s usually by training or by fluke. And it depends on how serious a question is at stake. As to the toes and similar tactics, a person’s strange reactions at miscellaneous points during the test only alert the examiner that he’s trying countermeasures in an effort to cover his lies.”
In Search of the Truth
Test-takers can use various techniques to cloud polygraph results. Such tricks would not necessarily clear them, however, only make their answers “questionable,” which could lead to further investigation. Aldrich H. Ames took two polygraphs at the CIA. In at least one, responses were such that the answers should have been referred to the FBI for follow-up. Industry experts cite studies showing polygraph validity rates as high as 95%.
How the machines work
The machine measures changes in pulse, blood pressure, fingertip perspiration, respiration and body movements during questioning.
Tactics to alter readings
* Psychological training can help test-taker manipulate answers.
* Curling toes and pressing feet down inside shoes on innocent questions can elevate readings, making entire test inconclusive.
* Some people have been known to put tacks in their shoes to elevate readings.
* Drugs--400 milligrams of meprobamate for example--can help test takers manipulate results.
Factors that affect accuracy
* Competence of examiner
* Psychological makeup of the examinee
* Context in which exam is given
Physical changes recorded on polygraph indicate when an individual might be lying. If the person tells the truth, little or no change is recorded.
Breathing (measured at diaphragm)
Breathing (measured at chest)
Blood pressure and heartbeat
Sources: Reuters, American Polygraph Assn., World Book Encyclopedia